1. Field of the Invention
The present invention relates to a flame retardant high impact polystyrene composition. More particularly, this invention relates to a flame retarded high impact polystyrene composition containing a flame retardant amount of a halophenoxyalkylsilane. Antimony oxide may also be present.
2. Description of the Prior Art
A variety of halophenoxyalkylsilanes are known to possess fire-retardant, fungicidal, phytotoxic, bactericidal and insecticidal properties. The preparation of these compounds have been reported in a number of U.S. patents and literature articles.
U.S. Pat. No. 3,492,328 teaches a process for the preparation of a halogenated tetraphenoxysilane of the formula ##STR1## wherein X represents fluorine, chlorine or bromine and n is a whole number of from 3 to 5. U.S. Pat. No. 3,546,267 also teaches a process for the preparation of halogenated phenoxysilanes. Further techniques on the preparation of these types of compounds is discussed in "(Halophenoxy)silanes VIII" by Ismail and Koetzsch in J. Organometal. Chem., 10 (1967) 421-426.
U.S. Pat. No. 3,509,090 claims the use of a wide variety of halogenated organosilane compounds as flame retardant additives in polycarbonate compositions. Examples 12 to 19 identify several other polymer systems where the halogenated organosilane compounds are effective flame retardants.
None of the above-identified references teach or suggest the use of any type of halogenated organosilane in high impact polystyrene (HIPS). The present invention claims the use of a flame retarding amount of a halophenoxyalkylsilane in high impact polystyrene. When a halophenoxyalkylsilane is incorporated in high impact polystyrene in the presence of antimony oxide as a synergist, the resulting formulation is not only flame retarded but retains Izod impact strength comparable to that shown by the original resin. Other flame retardants which are used in high impact polystyrene drastically reduce the impact strength of the composition. The halophenoxyalkylsilane flame retardants used in the practice of the present invention reduce the glow and increase char formation during burning while retaining good physical properties.